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Fencing calculations
A farmer has received a grant to fence off the river bank and install cattle troughs in the paddocks that are currently watered from the river. One of the best paddocks is an alluvial flat that forms a tongue of land in a bow of the river. The paddock is high enough above normal river height to have only minor inundation in a flood.
The riparian fence will allow native vegetation to be re-established on the riverbank. The vegetation and restrictions to stock access will help control stream bank erosion.
However, the farmer is concerned about weeds growing in the fenced off area. A gate in the riparian fence adjacent to the existing gate will allow access to the river bank for management and recreational purposes. It will also allow cattle to be moved into the riparian zone for crash grazing to help control weeds.
The farmer has drawn a map to scale so that the amount of materials can be calculated. The strainer posts in the existing fence will be used. Additional strainers and diagonal stays will be of hardwood. Steel posts at five metre (5 m) intervals will be used for the line posts. The gate will be of prefabricated steel, 3.6 metre (12 foot) in length. The fence will have four lines of high tensile barbed wire with a bottom line of plain high tensile wire to allow native animals safe passage to and from the river.
- Use the scale on the map to calculate the length of the fence.
- Determine the number of strainer posts required.
- Determine the number of diagonal stays required.
- Calculate the number of steel posts that will be needed.
- Calculate the required length of plain wire. Allow one extra metre to wrap and strain each end of every wire.
- Calculate the required length of barbed wire (don’t forget to allow one extra metre to wrap and strain each end of every wire).
- The barbed wire will be bought in 500 metre rolls. How many rolls of barbed wire are needed to complete the fence?
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